Dispersive Alfven waves are known to be one of the most important processes by which the magnetosphere and ionosphere are coupled. However the mechanisms by which shear and compressional modes are driven by equatorial processes is not well known. This project will develop a simulation model based on a reduced two-fluid MHD formulation (referred to as the four-field model) which incorporates parallel ion flow and compressibility to study the MI coupling via dispersive Alfven waves. The proposed research has two main targets: 1) to implement a nonlinear four-field model in computer simulation for Earth's magnetic field configuration to investigate effects of magnetospheric disturbances to the auroral ionosphere and 2) to develop the code in a highly modularized manner so that it can be coupled to other simulation models such as models for magnetic reconnection and ballooning instabilities. The four field model includes parallel ion flow in the formulation, and hence makes it possible to investigate MI coupling in the forms of mass and momentum transport in addition to transport of energy by Alfven wave Poynting flux. The code will be made into distributions (a package including the code itself, manual, change log, and other necessary information) so that researchers who would like to use it can download it and compile on their own platforms. The magnetospheric disturbances which are drivers of the simulation code can be taken from the output of magnetotail simulation models or satellite observations of the nightside magnetosphere. The code is expected to be eventually integrated into a Geospace General Circulation Model (GGCM). The tool can be equally useful in planetary sciences to study similar physical processes for other magnetized planets such as Jupiter. The proposal opens a venue for observers to contribute directly to numerical models by letting the observers run the code themselves so that they can provide input on how the model can be improved to better predict our geophysical environment. The open-usage policy has educational impacts because it will allow students new to the computer modeling of plasma processes a chance to look at the code themselves and modify the code to suit their own needs.
